A conventional circular polarizer is formed of a linear polarizer and a quarter-wave compensation film. The linear polarizer and the quarter-wave compensation film are stacked together at an angle of 45°. The quarter-wave compensation film is able to convert a linearly polarized light into a circularly polarized light. However, the quarter-wave compensation film is usually a narrowband phase retarder. That is, only at a specific spectrum a perfect circular polarization conversion can be achieved. Thereafter, it is hard to allow all the visible range of light, 400 to 700 nanometer (nm), to be converted to the polar point, the arctic, or an arctic region by using such a narrow-band quarter-wave compensation film, as a Poincare sphere optics was adopted.
Therefore, wideband compensation films are preferred for a favorable circular polarization conversion. There are two ways to manufacture the wideband compensation films, for example, a single-film type and a two-film type. It is known the single-film type requires very special material design, and the target retardation adjustment needs lots of work. The two-film type is more prevalent by simply stacking a half-wave compensation film and a quarter-wave compensation film and laminating together. However, particularly precise orientation is required for those compensation films in the two-film type, which means material waste and a large amount of labor cannot be avoided. Moreover, considering a mainstream requirement, thickness becomes a large issue either with a single-film type or a two-film type. Therefore, it has become a breakthrough requirement for the industries to provide a very thin wideband compensation stacked layer capable of covering the entire range of the visible light and is easy to manufacture.